Back in the “old days” when performance was always a concern, it made more sense. It was used in communication to verify integrity (do error checking) and a substantial portion of communication was serial, which makes more use of parity than parallel communications. In any case, it was trivial for the CPU to compute it … Read more
Carry Flag The rules for turning on the carry flag in binary/integer math are two: The carry flag is set if the addition of two numbers causes a carry out of the most significant (leftmost) bits added. 1111 + 0001 = 0000 (carry flag is turned on) The carry (borrow) flag is also set if … Read more
When you do a cmp a,b, the flags are set as if you had calculated a – b. Then the conditional jump instructions check those flags to see if the jump should be made. In other words, the first block of code you have (with my comments added): cmp al, dl ; set flags based … Read more